Move functions to BlockManager
Summary:
Needed for a later commit
This is a partial backport of core#23974
https://github.com/bitcoin/bitcoin/pull/23974/commits/fa88cfd3f9896d5b56ea6c111a23f90a79253c18
Test Plan: ninja all check-all
Reviewers: #bitcoin_abc, sdulfari
Reviewed By: #bitcoin_abc, sdulfari
Differential Revision: https://reviews.bitcoinabc.org/D12510